The present invention relates to a method of providing pixel information for a hard copy graphics presentation, and particularly to such a method requiring a minimum bit map memory space and operating in conjunction with a hard copy device to avoid delay in providing raster information.
In graphics display devices the information relative to objects for display may be received as a series of high level commands, each indicating the type of graphics object to be displayed and its position. Thus, such command may indicate a line is to be drawn including the origin of the line and its length in x and y coordinates. The graphics device then typically "pixelates" this information or "draws" elemental or dot portions of the line for entry into a pixel bit map memory. The pixel bit map memory is scanned or read out to provide an eventual display, using an ink jet copier or the like.
Conventionally, all of the commands would be received for the drawing of various objects, and all of these objects would be pixelated and "laid in" to a large bit map memory before the copier starts its operation. This involves a considerable delay in loading the bit map memory before hard copy print out can begin.
Although it is possible to portray a portion or strip of the display, thereby requiring a much smaller memory space for the bit map, nevertheless the whole bit map is ordinarily calculated or written before the presentation of each strip in order to be responsive to the graphics commands received. Thus, the bit map may be determined again and again, but only successive strips of the bit map would actually be "laid in" to the bit map memory. This involves considerable computing capability to provide the repeated bit map information.